The present invention relates to a motor vehicle with transmission and transmission fluid pump.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
A transmission fluid pump is provided to transport transmission oil to and within a transmission of the motor vehicle. A moving element of the transmission fluid pump is normally driven directly by the drive of the vehicle, typically the internal combustion engine. To design the transmission fluid pump as compact as possible, it has been proposed to merely convey sufficient oil, when the internal combustion engine operates at a middle to higher speed, but to cut the delivery of oil, when the internal combustion engine operates at a lower speed or in particular at idling speed. In order to deliver sufficient oil also when the internal combustion engine operates at idling speed, a further drive is provided to increase the speed of the pump when the idling speed is too low.
As the internal combustion engine and the additional drive, normally an electric motor, has to be coupled with the pump, the use of a summing gear set, in particular a planetary gear train, has been proposed. The moving element of the pump is hereby coupled with the summation shaft, i.e. the planet carrier, of the planetary gear train, when a simple planetary gear set is involved. The other components are coupled with the two drives, typically the ring gear with the internal combustion engine, when a simple planetary gear set is involved, and the sun gear with the electric motor.
When the internal combustion engine rotates faster than the electric motor, the sun gear is caused to move in relation to the planet carrier. This relative movement is undesired. Thus, the electric motor has to normally run continuously therewith so that the transmission fluid pump is operated by the internal combustion engine at the desired speed. There is thus room for saving energy when operating the electric motor.
It would therefore be desirable and advantageous to address prior art shortcomings and to allow operation of a transmission fluid pump for a motor vehicle at less energy.